Too cheap to have both? Please. A passport card costs $55 ($40 if you already have a passport book) and is valid for 10 years.
And why should I pay $55 for a duplicative document that serves no purpose, and that I’ll seldom use? I travel to Europe much more often than to Canada or Mexico.
Getting a passport card if you already have a passport book is throwing away money. I have no desire to waste money, whether it’s $4, $40, or $40,000. Frankly, I’d rather spend the money going out to eat — a passport card isn’t very tasty last I checked.